Various abbreviations that appear in the specification and/or in the drawing figures are defined as follows:
DFS dynamic frequency scaling
DVS dynamic voltage scaling
DVFS dynamic voltage and frequency scaling
HW hardware
OP operating point
PM power management
PPD peripheral power domain
PSS processor subsystem
SC system control
SW software
The OP may be considered as some particular functional performance point for a system or subsystem, and may be considered to represent a combination of clock frequencies and operating voltages that are in use.
In some current ASIC design architectures the various subsystem and/or system performance control methods are embodied in SW layers, while the HW simply provides a mechanism to control the system performance in frequency, i.e., clock frequency, and voltage. For example, to achieve frequency and voltage control the SW may be responsible for determining a level of desired performance and for mapping the determined level of system performance into different subsystem performance states. The result of this processing by the SW is then passed to the HW to effect the indicated changes in the clock frequency and/or power supply output voltage levels.
It should be noted that the frequency and/or voltage control function may need to be accomplished during runtime, and thus should ideally be accomplished with minimal latency. However, this may be difficult to accomplish if the system SW is engaged in other runtime-related tasks.
WO 2005/050425 A1 describes a device for regulating a voltage supply to a semiconductor device. The device has memory for storing a plurality of performance ranges, where respective performance ranges are associated with a respective supply voltage. The device also includes a measurement unit for measuring the performance of the semiconductor device and a regulator for modifying the supply voltage to the semiconductor device if the measured performance of the semiconductor device is not within a predetermined portion of the performance range associated with the voltage supplied to the semiconductor device. A set of reference circuit count values is stored in a look-up table, where each set of reference circuit count values is associated with a respective supply voltage.
What is needed is a technique to enable accurate, simple and low latency control of frequency and voltage in an integrated circuit environment.